In general, color photographic images are formed by processing a silver halide color photographic material as follows. First, the color photographic material is imagewise exposed and developed by a developing composition containing a color developing agent. In this case, the silver halide at the exposed portions is reduced to silver and at the same time, the color developing agent is oxidized. The oxidized color developing agent thus formed causes coupling with couplers contained in the color photographic material to imagewise form dyes corresponding to developed silver. It is known that a p-phenylenediamine derivative is used as the color developing agent for obtaining color images by utilizing the oxidative power of the exposed silver halide.
A color developing composition being used for performing the aforesaid color development generally contains 1) a color developing agent, 2) a preservative for preventing the color developing agent from being deteriorated by air oxidation, such as sodium sulfite, hydroxylamine, etc., 3) a buffer for stabilizing the developing composition at high pH for obtaining a high developing activity, 4) an antifoggant, 5) benzyl alcohol for accelerating the coupling reaction, etc. Also, as the case may be, the color developing composition contains a polyethylene glycol, a surface active agent, an auxiliary developing agent, etc.
A color developing agent excluding benzyl alcohol which has hitherto been used for accelerating development has recently been particularly desired from the viewpoint of a pollution countermeasure. However, when a color photographic material is deeloped by a color developer containing a known color developing agent without using benzyl alcohol, the density of images formed is extremely reduced. Accordingly, it has been keenly desired to find a color developing agent which can give dyes having sufficiently high density regardless of the presence or absence of benzyl alcohol.
Also, in the color development step, all the silver halide grains having latent images do not always relate to the formation of dyes at color development. So-called "dead grains" are wasted in a color photographic development. Accordingly, a new color developing agent capable of forming a dye at a larger ratio to the amount of exposed silver halide than that attained by a conventional color developing agent has been required. If silver halide grains are effectively converted to silver and then a dye is effectively formed, the amount of silver being used may be less and the thickness of the photographic emulsion layers of a color photographic light-sensitive material can be reduced, which gives various advantages, that is, a quick development process can be applied and color images having high resolving power are obtained.
Also, for sufficiently increasing the density of dyes formed by development, it is most advantageous to increase the extinction coefficient of the dyes formed. If a new color developing agent giving a dye having a far larger extinction coefficient than that of a dye formed from a conventional color developing agent is obtained, it becomes possible to reduce the amount of couplers in a color photographic material and to reduce the thickness of the photographic emulsion layers of a color photographic material.
Also, in regard to the color reproduction of color images formed by development, the color images of dyes formed using a conventional color developing agent are insufficient in color reproduction since the absorption of the dye is boad and a side absorption exists in the color images. In particular, the absorption of a cyan dye formed from a cyan formed by coupler (cyan coupler) and a color developing agent is broad and hence the discovery of a new color developing agent giving a cyan dye having a sharp absorption has been desired.
On the other hand, a color developer is unstable and the composition of a color developer is liable to change during the storage thereof, whereby the management of a color developer is difficult. Accordingly, it has recently been proposed to incorporate a color developing agent in a silver halide color photographic material. By incorporating a color developing agent in a color photographic material, the composition of a color developer is simplified and the management of the color developer becomes easy. Also, in this case, the color photographic material can be developed by an alkaline bath only, which is very useful for the simplification and quickening of processing.
However, when a p-phenylenediamine series developing agent is incorporated in a color photographic material, there occur problems that the color photographic material is liable to cause desensitization, fog, or stains during the storage thereof. Thus, a system of incorporating a precursor for the color developing agent in a color developing material for increasing the stability of the color developing agent in the color photographic material during the storage thereof has been proposed.
For example, Schiff base type precursors for color developing agents are disclosed in U.S. Pat. No. 3,342,599 and JP-A-56-106241, JP-A-56-107236 and JP-A-56-123534 (the term "JP-A" as used herein refers to a "published unexamined Japanese patent application"). Also, sulfonylethylurethane type precursors are disclosed in JP-B-58-14671 (the term "JP-B" as used herein refers to an "examined Japanese patent publication"), cyanoethylurethane type precursors are disclosed in JP-B-58-14672, arylurethane type precursors are disclosed in JP-A-58-95344, JP-A-61-113059, and JP-A-61-114238, and arylurea type precursors are disclosed in JP-A-59-53931.
By the aforesaid techniques, it becomes possible to incorporate a p-phenylenediamine series color developing agent in a color photographic material but there remains a large problem that has not yet been solved.
That is, the color developing agent precursors used in these conventional techniques are all the precursors for conventionally known color developing agents and these precursors have the problems of the conventionally known color developing agents as they are. For example, there are problems that when the color photographic material contains such a precursor with an activator solution witnout containing benzyl alcohol, the density of color images formed is greatly reduced, the ratio of dyes formed to the exposed silver halide is yet low, the extinction coefficient of dyes formed is yet low, and the absorption of a dye formed is broad. Thus, it has been keenly desired to discover precursors for color developing agents having no such problems of the conventionally known color developing agents.
Also, a system of incorporating a color developing agent in a light-sensitive material and obtaining color images through a heat development step is known in JP-A-59-12431. JP-A-59-116642, JP-A-59-116643 and JP-A-59-116740.
The heat developable light-sensitive material can be composed of 1) a color developing agent, 2) a light-sensitive silver halide, and 3) a dye providing material but, if desired, an organic silver salt can be used. In this case, a dye is formed or released from the dye providing material as a function of the reduction of the light-sensitive silver halide and/or the organic silver salt.
In the aforesaid system, a system shown below has been actively investigated recently.
That is, a heat developable light-sensitive material in the system is composed of 1) an organic silver oxidizing agent stable to light, 2) a color developing agent, 3) a silver halide which becomes a catalyst for an oxidation reduction reaction of the organic silver oxidizing agent and the color developing agent at heat development when the silver halide is light exposed, 4) a material providing a dye by causing a reaction with the oxidation product of the color developing agent, 5) a binder, and 6) a support.
In general, the aforesaid heat developable light-sensitive material forms color images by the following manner. When the exposed heat developable light-sensitive material is heat developed, an oxidation reduction reaction occurs between the organic silver salt oxidizing agent and the color developing agent with the exposed light-sensitive silver halide as a catalyst to form silver images at the exposed portions. In this case, the color developing agent is simultaneously converted into the oxidation product thereof and the oxidation product causes a coupling reaction with the dye providing material to form color images as a function of the reduction of the organic silver salt oxidizing agent.
In the color developing agent which is used for the aforesaid heat developable light-sensitive material, there also exists the same problems as in the case of the color developing agent which is used for the aforesaid color developing composition. That is, a color developing agent giving a larger ratio of the dye formed to the organic silver salt oxidizing agent or to the exposed silver halide than that of a conventionally used color developing agent has been required.
Furthermore, for sufficiently increasing the density of color images formed, the discovery of a color developing agent giving a dye having a far larger extinction coefficient than dyes formed by using conventional color developing agents has been strongly desired.
Also, in regard to the color reproduction of color images formed by development, the discovery of a color developing agent giving a dye having a sharper absorption has been strongly desired.
Now, color developing agents capable of being developed by a developer containing no benzyl alcohol from the viewpoint of avoiding the occurrence of pollution are disclosed in JP-A-52-134432, JP-A-52-76032, JP-A-51-95849, and JP-A-50-131526. However, it cannot be said that a sufficient dye density is obtained by using these color developing agents. Also, the ratio of the dye density formed at color developing latent images to the density of developed silver formed simultaneously is yet low. One of the reasons is that the extinction coefficient of the dye formed by coupling is low. Furthermore, these conventional color developing agents have a disadvantage that the absorption of dyes formed is broad.
Moreover, since conventionally known precursors for color developing agents which can be used in a color photographic light-sensitive material are precursors for conventionally known color developing agents only, these precursors have the aforesaid problems of the conventionally known color developing agents as they are.
Furthermore, the similar problems exist in the case of using these color developing agents for a heat developable light-sensitive material. For example, heat developable light-sensitive materials using p-phenylenediamine derivative series color developing agents are disclosed in JP-A-59-57237, JP-A-56-146133, JP-A-59-116740, and JP-A-63-301037 but in the case of using these color developing agents or the precursors thereof, a sufficient dye density is not obtained. Also, in these cases, there are various problems that the ratio of a dye formed by color development to the organic silver salt oxidizing agent or the exposed silver halide is yet low, the extinction coefficient of the dye formed is small, an the absorption of the dye formed is broad.